Evaluation of coronary stenoses experimentally and clinically hampered by the absence of satisfactory criteria for defining the severity of coronary lesions. The use of percent diameter narrowing does not account for the critical geometric characteristics of stenosis length, absolute diameter, eccentricity and shape or streamlining which may have greater effects on pressure and flow than percent stenosis. Accordingly, there are no means of comparing stenoses of differing size and shape or in different sized coronary arteries and there is no way of defining how severe a lesion must be geometrically before causing regional underperfusion, abnormal left ventricular contraction, or ischemia. Model constrictions of rigid tubes have been described by fluid dynamic equations relating geometric characteristics to flow velocity and pressure loss. However, the applicability of these fluid dynamic equations to stenoses of an artery with pulsatile pressure and flow and a distensible, vasoactive vessel wall has not been demonstrated in vivo. Over the past four years the principal investigator has developed a chronically instrumented dog model for coronary arteriography and independent measurement of the pressure gradient-flow characteristics of variable, controlled coronary stenoses in intact, unsedated dogs. In addition, the first method for quantitative coronary arteriography was developed at this University. Preliminary results in this laboratory indicate that quantitative analysis of orthogonal coronary arteriograms using classical fluid dynamic equations accurately predicts the experimentally measured pressure gradient-flow characteristics of coronary stenoses. The goals of this project are to complete these preliminary studies validating the accuracy of quantitative coronary arteriography for predicting the pressure flow characteristics of coronary stenoses. The results would document the applicability of basic fluid dynamic equations to coronary stenoses in vivo and would provide a radiologic "gold standard" for defining severity of arterial stenoses for clinical and experimental purposes.